'\" et
.TH LOGGER "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
logger
\(em log messages
.SH SYNOPSIS
.LP
.nf
logger \fIstring\fR...
.fi
.SH DESCRIPTION
The
.IR logger
utility saves a message, in an unspecified manner and format,
containing the
.IR string
operands provided by the user. The messages are expected to be
evaluated later by personnel performing system administration tasks.
.P
It is implementation-defined whether messages written in locales
other than the POSIX locale are effective.
.SH OPTIONS
None.
.SH OPERANDS
The following operand shall be supported:
.IP "\fIstring\fR" 10
One of the string arguments whose contents are concatenated together,
in the order specified, separated by single
<space>
characters.
.SH STDIN
Not used.
.SH "INPUT FILES"
None.
.SH "ENVIRONMENT VARIABLES"
The following environment variables shall affect the execution of
.IR logger :
.IP "\fILANG\fP" 10
Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 8.2" ", " "Internationalization Variables"
for the precedence of internationalization variables used to determine
the values of locale categories.)
.IP "\fILC_ALL\fP" 10
If set to a non-empty string value, override the values of all the
other internationalization variables.
.IP "\fILC_CTYPE\fP" 10
Determine the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments).
.IP "\fILC_MESSAGES\fP" 10
.br
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error. (This means
diagnostics from
.IR logger
to the user or application, not diagnostic messages that the user is
sending to the system administrator.)
.IP "\fINLSPATH\fP" 10
Determine the location of message catalogs for the processing of
.IR LC_MESSAGES .
.SH "ASYNCHRONOUS EVENTS"
Default.
.SH STDOUT
Not used.
.SH STDERR
The standard error shall be used only for diagnostic messages.
.SH "OUTPUT FILES"
Unspecified.
.SH "EXTENDED DESCRIPTION"
None.
.SH "EXIT STATUS"
The following exit values shall be returned:
.IP "\00" 6
Successful completion.
.IP >0 6
An error occurred.
.SH "CONSEQUENCES OF ERRORS"
Default.
.LP
.IR "The following sections are informative."
.SH "APPLICATION USAGE"
This utility allows logging of information for later use by a system
administrator or programmer in determining why non-interactive
utilities have failed. The locations of the saved messages, their
format, and retention period are all unspecified. There is no method
for a conforming application to read messages, once written.
.SH EXAMPLES
A batch application, running non-interactively, tries to read a
configuration file and fails; it may attempt to notify the system
administrator with:
.sp
.RS 4
.nf

logger myname: unable to read file foo. [timestamp]
.fi
.P
.RE
.SH RATIONALE
The standard developers believed strongly that some method of alerting
administrators to errors was necessary. The obvious example is a batch
utility, running non-interactively, that is unable to read its
configuration files or that is unable to create or write its results
file. However, the standard developers did not wish to define the
format or delivery mechanisms as they have historically been (and will
probably continue to be) very system-specific, as well as involving
functionality clearly outside the scope of this volume of POSIX.1\(hy2017.
.P
The text with
.IR LC_MESSAGES
about diagnostic messages means diagnostics from
.IR logger
to the user or application, not diagnostic messages that the user is
sending to the system administrator.
.P
Multiple
.IR string
arguments are allowed, similar to
.IR echo ,
for ease-of-use.
.P
Like the utilities
.IR mailx
and
.IR lp ,
.IR logger
is admittedly difficult to test. This was not deemed sufficient
justification to exclude these utilities from this volume of POSIX.1\(hy2017. It is also
arguable that they are, in fact, testable, but that the tests
themselves are not portable.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIlp\fR\^",
.IR "\fImailx\fR\^",
.IR "\fIwrite\fR\^"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "Chapter 8" ", " "Environment Variables"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
